1. Field of the Invention
The present invention relates to a metal fixture to be embedded in a dust cover so that the dust cover is attached to the installation place of a counterpart object.
2. Description of Conventional Art
As shown in FIG. 5, a dust cover 52 is commonly used for protectively sealing a swing mechanism of a ball joint 51, and a metal fixture 54 is embedded in the dust cover 52 at an outer periphery thereof so that the dust cover 52 is attached to a joint socket 53 as the counterpart of the dust cover 52 (refer to Patent Documents 1, 2, 3 and 4).
As shown in FIG. 6 in an enlarged scale, the metal fixture 54 is formed by press working, and the metal fixture 54 comprises an annular base portion 55 made by folding back of a metal sheet to have an approximately U-shape in cross section, and an inward peripheral tooth 56 formed at the inner circumference side of the base 55. The inward peripheral tooth 56 is formed integrally with the base 55 in a frustum shape in order to provide a fitting margin with respect to the joint socket 53.
Further, as shown in FIG. 7, when the dust cover made of a rubber-like elastic material is formed by means of a formation mold 57, the metal fixture 54 is inserted into the mold 57 and embedded into the dust cover 52 simultaneously with the formation of the dust cover 52 (insert molding).
Further, as shown in FIG. 6, the metal fixture 54 is embedded in the dust cover 52 at such a position that is apart in the axial direction from the end portion 52a at a distance d. Therefore, as shown in FIG. 7, a plurality of pins 58 are provided upright on the inner surface of the mold 57 to define the height position of metal fixture 54 such that the metal fixture 54 is disposed at a predetermined height position when the metal fixture 54 is inserted in the mold 57. Therefore, when the dust cover 52 is taken out from the mold 57 after the completion of molding, a plurality of concavities 59 are formed at the end face 52a of the dust cover 52 as a result of the pins 58 being pulled out, as the dust cover 52 is formed with the metal fixture 54 mounted on the pins 58.
However, the above-mentioned conventional art has some disadvantages as follows.
The annular base portion 55 of metal fixture 54 is made by folding back of a metal sheet to have an approximately U-shape in cross section as described above to maintain a predetermined mechanical strength, and thus has a volume of two layers of a metal sheet due to that shape. Therefore, there is disadvantage that weight of the metal fixture 54 as a whole is heavy. Recently, weight saving of components is carried forward rapidly in the industrial field of automobile and other general industrial machineries, and a dust cover 52 is not regarded as an exception.
Further, there is inconvenience that the mold has a complicated structure and thereby much labor and time are required for the maintenance of the mold, since a plurality of pins 58 are provided uprightly in the forming mold 57 as height position defining means of the metal fixture as described above.
The conventional arts are disclosed in, for example, Japanese unexamined utility model publication No. H01-92518, Japanese unexamined patent publication No. S62-56866, Japanese unexamined patent publication No. S62-80014, and Japanese unexamined utility model publication No. H04-34510.